The Buy1 Buy2 Buy3 volume discount display on item pages does not indicate that different items can be purchased to get the discount. Buyers are under the impression that have to buy 2+ of the same item.
Volume pricing Note: Volume pricing discounts are applied on all orders of 2,3,4+ of any items in the same Volume pricing campaign.For example, if item A and B are in the same campaign, then the offer will apply to an order of 2x item A or 3x item B, as well as 1x item A and 1x item B.Ensure that items in this campaign are a good fit for the same discount when combined.